1. Field of the Invention
The present invention relates to an apparatus for the recovery of heat from a steam boiler, and more particularly to a unit which is useful in connection with a steam boiler to recover heat from the blowdown water.
2. Description of the Prior Art
A variety of devices and apparatus have been proposed in the prior art for measuring the amount of heat which is delivered to or received from a device. For example, in U.S. Pat. No. 4,250,747, issued to Diprose et al. on Feb. 17, 1981, there is disclosed a device for use with a hot water radiator system which measures the radiation from the system in units of 0.1 kilowatt-hours. The Diprose patent uses a flow rate measurement and two electrical resistance thermometers to determine the heat which is supplied by a radiator system, particularly for a hot water radiator system. The Diprose device is indicated for use with any electrically conductive fluid, including an electrolytic slurry.
Other systems which also include temperature sensors and flowmeters and provide a reading of heat in terms of units proportional to BTU's are disclosed in the U.S. Pat. Nos. 4,048,852, issued to Sakakibara et al. on Sept. 20, 1977 and 3,971,252, issued to Onoda on July 27, 1976. In the Sakakibara device, there is used a rotating vein flow meter with intermittent measurement being used after a predetermined volume of flow. The read out is only proportional to the heat supplied, such as a value of temperature differential times the number of units of volume, and the purpose is expressed as a low power requirement enabling battery operation. The Sakakibara patent describes an apparatus for the measurement of heat energy from supply equipment and heat used by load equipment, and particularly describes a measurement of heat supplied to dwellings in a housing area. The Onoda patent describes an electronic integration colorimeter which employs an impeller flowmeter, and the read out is in proportion to the production of heat. The Onoda patent provides a system for measuring the heat absorbed or provided by cooling or heating fluid passing through a device such as an air conditioner.
Devices have also been proposed in the prior art which include temperature sensing and flow metering coupled with a reading of heat supplied or received in terms of BTU's. Examples of such devices are contained in U.S. Pat. Nos. 4,224,825, issued to Feller on Sept. 30, 1980; 3,593,578, issued to Farrell on July 20, 1971; and 3,301,049, issued to Meyerson on Jan. 31, 1967. The Feller patent describes the measurement of heat absorbed by a solar heat absorber. The Feller device is apparently most interested in solar heating efficiency with the primary feature being to compensate for temperature dependent variables in density and specific heat. The read outs for the Feller unit are in heat absorbed over a period of time, or heat absorbed per unit of time, and there is stress as to the circuitry employed to compensate for temperature dependencies. The Farrell patent has a particular purpose in improved temperature sensing, and gives read outs of temperature, BTU's and flow in gallons. The Farrell patent provides a mechanical metering system which measures the heat transferred relative to a heat device such as a heat exchanger. The Meyerson device uses a standard drive shaft flowmeter, and gives a read out as to temperature difference, BTU output and flow in gallons. The metering of heat supplied or removed by a heating or cooling device, in particular measuring the heat radiated as the primary use of the device, is described in the Meyerson patent.
In the field of steam boilers, it is known in the prior art that the water within the boiler which remains after steam has been generated will receive a concentrating effect of the minerals and other contaminants of the water which will not pass into the steam phase. It is therefore the practice to periodically "blowdown" this dirty water in order to minimize this concentrating effect. This blowdown water is replaced with clean or fresh water which naturally is cooler than the water which was in the boiler. It is therefore also the practice in the prior art to pass this blowdown water through a heat exchanger to impart some of this heat to the fresh water which is being added to the boiler. Blowdown control systems are known which will blowdown or eliminate a certain amount of boiler water in response to a monitoring of the conditions within the boiler. These units may include a flowmeter to indicate the flow of the blowdown water from the boiler.
In contrast, the present invention provides a unit which readily and advantageously accomplishes several functions and does so in an economical and convenient fashion. Unlike the prior art devices such as those described, the present invention provides for a measurement of the flow rate and volume of blowdown water and replacement water, and also a measurement of the heat energy transferred from the blowdown water to the fresh water, particularly in units of BTU's.